NBDHE Study Guide — 2026 Edition

Periodontal disease is the center of gravity of dental hygiene practice — and of this examination. This chapter covers its etiology and pathogenesis, the 2017 classification, risk factors, assessment, nonsurgical therapy, adjunctive and surgical therapy, maintenance, and the preventive agents (fluoride, sealants, antimicrobials) that keep disease from starting.

Etiology and pathogenesis

Periodontal disease begins with the plaque biofilm (Chapter 2). Bacterial products trigger an inflammatory response in the gingiva — gingivitis: red, swollen gums that bleed easily. If the biofilm is not removed, inflammation extends into the supporting tissues: the periodontal ligament and alveolar bone are destroyed, the gingiva separates from the tooth forming a periodontal pocket, and attachment is lost — periodontitis. The host response does the destroying: enzymes and inflammatory mediators released to fight bacteria break down collagen and bone. That is why two patients with similar plaque levels can have very different disease severity — risk factors modulate the host response.

Risk factors

The major modifiable risk factors are tobacco use and diabetes (poor glycemic control worsens disease and its treatment response); others include poor oral hygiene, stress, certain medications (causing gingival enlargement or xerostomia), and genetic susceptibility. Risk assessment shapes both the diagnosis (grading) and the treatment plan.

Classification: the 2017 World Workshop system

The current classification stages and grades periodontitis:

• Staging describes severity and extent: it starts from clinical attachment loss (CAL) at the site of greatest loss, then incorporates probing depths, furcation involvement, tooth mobility, and radiographic bone loss. Higher stages mean more severe disease and more complex management.
• Grading indicates the rate of progression, responsiveness to standard therapy, and potential impact on systemic health. Clinicians initially assume grade B (moderate rate) and seek specific evidence to shift to grade A (slow) or grade C (rapid) — for example, heavy smoking or poorly controlled diabetes pushes toward grade C.

Necrotizing periodontal diseases and periodontitis as a manifestation of systemic disease are separate categories. Peri-implant diseases (mucositis, peri-implantitis) are classified alongside.

How it is tested: "stage vs. grade" sorting questions, CAL-based staging scenarios, and grade-modifier questions (smoking, HbA1c). The trap: confusing staging (how bad is it now) with grading (how fast is it moving).

Assessment

A complete periodontal assessment includes: probing depths at six sites per tooth, CAL (probing depth plus recession — the true measure of attachment), bleeding on probing, suppuration, furcation involvement, mobility, the width of keratinized tissue where relevant, and radiographic bone levels. Bleeding on probing signals active inflammation; its absence is a strong indicator of stability.

Nonsurgical periodontal therapy

Scaling and root planing (SRP) — a deep cleaning of the affected tooth and root surfaces — is the cornerstone of initial therapy: remove plaque, calculus, and contaminated cementum/dentin so the tissues can heal. It is performed with hand instruments, ultrasonic scalers, or both. Re-evaluation follows in 4–6 weeks: sites that have resolved go to maintenance; residual deep pockets may need further treatment.

Adjunctive therapy includes locally delivered antimicrobials placed in residual pockets and, in selected cases, systemic antibiotics — adjuncts to mechanical therapy, never substitutes. Host-modulation (e.g., subantimicrobial-dose doxycycline) is another adjunct category.

Surgical therapy (flap procedures, osseous resection, regenerative techniques, grafting) is indicated when nonsurgical therapy cannot resolve the disease — but the exam emphasizes that surgery is the dentist's/periodontist's domain; the hygienist's role is assessment, nonsurgical therapy, and maintenance.

Periodontal maintenance

After active therapy, the patient enters maintenance (supportive periodontal therapy): recall intervals based on risk (often every 3–4 months for periodontitis patients), with probing, debridement of recurrent deposits, and reinforcement of home care. Maintenance is lifelong — without it, disease recurs.

Preventive agents

• Fluoride: the cornerstone caries-preventive agent. Community water fluoridation reduces dental caries by approximately 25% in children and adults; water systems target 0.7 mg/L (maintaining ≥0.6 mg/L), with an EPA safety standard of 2.0 mg/L to prevent mild or moderate dental fluorosis. Topical fluorides (varnish, gel, foam, rinses, toothpaste) promote remineralization and inhibit demineralization. Fluoride varnish is the preferred professional topical for young children and high-risk patients.
• Sealants: pit-and-fissure sealants are a physical barrier — multiple studies confirm the reduction of pit and fissure carious lesions with their placement. They are not a chemical treatment — retention must be checked.
• Antimicrobials: chlorhexidine rinses reduce plaque and gingivitis short-term (staining and taste alteration limit long-term use); essential-oil rinses are adjuncts to mechanical cleaning, not replacements.
• Xylitol and other agents: sugar substitutes that reduce cariogenic bacterial load; evidence supports them as adjuncts within a comprehensive prevention plan.

How it is tested: mechanism questions (how fluoride works), application questions (which agent for which patient), sealant indications and retention checks, and "which is the best next step" therapy sequences. The trap: recommending a sealant over an existing carious lesion without addressing the caries, or substituting a rinse for mechanical plaque removal.

Staging and grading: the table values

Stage by interdental CAL at the worst site: 1–2 mm stage I, 3–4 mm stage II, 5 mm or more stages III–IV^[1]. Radiographic bone loss extending to the middle third of the root places the case at stage III or IV^[1], and tooth loss separates them: 4 or fewer teeth for stage III, 5 or more for stage IV^[1]. Extent is localized when fewer than 30% of teeth are involved^[1]. Grade by direct evidence over five years (no loss, under 2 mm, 2 mm or more)^[1], or by percentage bone loss divided by age (under 0.25, 0.25–1.0, over 1.0)^[1]; modifiers are smoking (under 10 a day grade B, 10 or more grade C)^[2] and HbA1c (under 7.0% grade B, 7.0% or more grade C)^{[1, 2]}.

Fluoride safety and sealant technique

Dental fluorosis comes from excess fluoride during tooth-forming years, before about age 8^[3]; the EPA's 2.0 mg/L standard prevents mild or moderate fluorosis and its 4.0 mg/L maximum prevents bone disease^{[3, 4]}. Resin sealant retention depends on proper etching and a dry field^[5]; etching removes about 10 microns of enamel and pumice about 4^[5]. Sealing incipient lesions inhibits them^[5], and non-cavitated surfaces need no tooth structure removed^[5]. School programs should seal children even if a retention check cannot be guaranteed^[5].

Key numbers

• Stage by CAL: 1–2 / 3–4 / ≥5 mm^[1]; localized under 30% of teeth^[1].
• Grade by bone loss ÷ age: <0.25 / 0.25–1.0 / >1.0^[1].
• Fluorosis window: before about age 8^[3].
• Community water fluoridation: ~25% caries reduction; target 0.7 mg/L; EPA safety standard 2.0 mg/L (fluorosis prevention).
• Sealants reduce pit-and-fissure carious lesions; retention must be checked.
• Grading: default Grade B; Grade A slow, Grade C rapid progression.
• Re-evaluate nonsurgical therapy in 4–6 weeks; maintenance often every 3–4 months for periodontitis patients.

Key takeaways

• Gingivitis is reversible inflammation; periodontitis is irreversible attachment and bone loss driven by the host response to the biofilm.
• Stage = severity/extent (from CAL at the worst site); Grade = rate of progression and treatment responsiveness (default B).
• Tobacco and poorly controlled diabetes are the key grade modifiers and treatment-response predictors.
• SRP is the cornerstone of initial therapy; re-evaluate in 4–6 weeks; maintenance is lifelong.
• Fluoride (~25% caries reduction from water fluoridation), sealants, and antimicrobials are adjuncts to — never replacements for — mechanical plaque control.

Chapter 5 Quiz

1. Which statement best distinguishes gingivitis from periodontitis?

• A. Gingivitis is reversible; periodontitis has attachment loss
• B. Both are irreversible once bleeding on probing is present
• C. Gingivitis is viral; periodontitis is fungal
• D. Gingivitis involves bone loss; periodontitis affects only gingiva

2. In the 2017 classification, periodontitis staging begins with which measurement?

• A. Number of missing teeth regardless of cause
• B. Clinical attachment loss at the greatest-loss site
• C. Patient-reported pain intensity at the worst tooth
• D. Salivary flow rate averaged over the dentition

3. What does grading of periodontitis aim to indicate?

• A. Number of teeth requiring extraction
• B. Patient age at diagnosis
• C. The cost category used for insurance billing
• D. Progression rate, therapy response, systemic impact

4. When grading a new periodontitis case with no prior records, what should the clinician initially assume?

• A. Grade C disease, downgrading only after five stable years
• B. No grade without ten years of radiographs
• C. Default to grade B; shift only with evidence
• D. Grade A disease, upgrading only if treatment fails

5. Which finding would support shifting a periodontitis grade from B toward C?

• A. Well-controlled diabetes with no smoking history at all
• B. Complete smoking abstinence and HbA1c maintained below 7.0%
• C. No systemic disease and no history of tobacco use
• D. Smoking ≥10 cigarettes/day; HbA1c ≥7.0%

6. A patient presents with 5-mm probing depths, bleeding on probing, and 3 mm of clinical attachment loss on the molars. What does the CAL value primarily indicate?

• A. True attachment loss regardless of gingival position
• B. The depth of the gingival sulcus in health
• C. The amount of enamel remaining on the crown
• D. The patient's pain tolerance during probing

7. Scaling and root planing is best described as which of the following?

• A. A cosmetic polishing of the visible clinical crowns
• B. An orthodontic procedure to reposition misaligned teeth
• C. A surgical procedure that removes diseased alveolar bone tissue
• D. A deep cleaning of affected tooth and root surfaces

8. According to the National Institute of Dental and Craniofacial Research, what does any type of gum disease treatment require of the patient?

• A. Good daily home oral health care
• B. That the patient stop using fluoride during treatment
• C. That the patient avoid brushing until all treatment is finished
• D. That all home care be performed by the dentist instead

9. Which statement about adjunctive antimicrobial therapy in periodontitis is most accurate?

• A. It replaces scaling and root planing in deep pockets
• B. It is effective as a sole therapy without debridement
• C. An adjunct to mechanical therapy, not a substitute
• D. It eliminates the need for periodontal maintenance

10. In advanced cases of gum disease, which treatment may be required?

• A. Antibiotics alone with no debridement
• B. Observation only, since advanced disease is untreatable
• C. Extraction of all teeth as the first step
• D. Surgical treatment

11. Community water fluoridation reduces dental caries by approximately how much?

• A. 90% in all age groups
• B. 25% in children and adults
• C. 5% in children only
• D. 50% in adults only

12. What fluoride level should community water systems target?

• A. 0.1 mg/L with no minimum level
• B. 0.7 mg/L; maintain ≥0.6 mg/L
• C. 2.0 mg/L as the recommended target
• D. 5.0 mg/L for the maximum benefit

13. The EPA safety standard for fluoride in drinking water is set at 2.0 mg/L to prevent which condition?

• A. Mild or moderate dental fluorosis
• B. Thyroid enlargement in children
• C. Kidney stones in all age groups
• D. Skeletal fractures in older adults

14. Dental sealants are most strongly indicated for which teeth and why?

• A. All teeth equally, because caries risk is uniform across the dentition
• B. Permanent molars, where studies confirm lesion reduction
• C. Anterior teeth, because they are the most visible when smiling
• D. Primary incisors, because they are the first teeth to exfoliate

15. A sealant was placed six months ago and is now partially lost on one molar. What is the appropriate action?

• A. Leave it, because partial sealants still fully protect
• B. Assess the tooth for caries and repair or replace the sealant
• C. Extract the tooth to prevent future caries
• D. Apply fluoride varnish over the partial sealant and never recheck it

16. A patient with open interproximal spaces asks what to use between her teeth besides floss. Which option does NIDCR mention?

• A. A hard-bristled brush used with force
• B. An alcohol rinse instead of cleaning
• C. A toothpick used once a week
• D. An interdental brush or water flosser

17. Bleeding on probing at a maintenance visit most directly indicates which of the following?

• A. An allergic reaction to the probe
• B. Complete periodontal stability
• C. Active inflammation at bleeding sites
• D. A need for immediate surgical therapy

18. Which patient factor most worsens the expected response to standard periodontal therapy?

• A. Well-controlled hypertension
• B. Mild seasonal allergies
• C. Poorly controlled diabetes
• D. A vegetarian diet

Sources cited in this excerpt

1. Staging and Grading Periodontitis (2017 World Workshop). American Academy of Periodontology. http://perio.org/wp-content/uploads/2019/08/Staging-and-Grading-Periodontitis.pdf
2. Staging and Grading Periodontitis (2017 World Workshop). http://perio.org/wp-content/uploads/2019/08/Staging-and-Grading-Periodontitis.pdf
3. Community Water Fluoridation — MMWR report. Centers for Disease Control and Prevention (MMWR). https://pmc.ncbi.nlm.nih.gov/articles/PMC10243485/
4. Community Water Fluoridation — MMWR report. https://www.ncbi.nlm.nih.gov/pmc/
5. Pit and Fissure Sealants: Utilization considerations. Dentalcare.com continuing-education course. https://www.dentalcare.com/en-us/ce-courses/ce673/sealant-utilization-considerations